<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;
      height: 100px;
      border: 6px solid red;
        /*设置圆角 值月大越圆 超过宽高的一半为正圆*/
        border-radius: 100px;
    }
    #d2{
        width: 100px;
        height: 100px;
        border: 1px solid blue;
        /*默认情况下给元素添加内边距会影响元素的宽高*/
        padding-left: 50px;
        padding-top: 50px;
        /*设置添加内边距不影响宽高*/
        box-sizing: border-box;
    }
    body{
        margin: 0;/*去掉自带的外边距*/
    }
  </style>
</head>
<body>
<h1>这是h1</h1>
<div id="d2">内边距</div>
<div id="d1">边框测试</div>
<p>这是p标签</p>
<ul>
    <li>aaa</li>
    <li>bbb</li>
    <li>ccc</li>
</ul>
</body>
</html>